Streptococcus pneumoniae is a leading cause of global morbidity and mortality, resulting in 1.5 million deaths every year worldwide, for example, from pneumonia, bacteremia, meningitis, and otitis media primarily in children <5 years old.
Successful polysaccharide vaccines are available in the United States. However, countries with limited resources cannot afford these vaccines. The current vaccines (23-valent polysaccharide (adults); and 7-valent polysaccharide (children)) protect against more prevalent serotypes. There are 90 known serotypes of Streptococcus pneumoniae. However there is a need for a vaccine that protects against all known serotypes. Pneumococcal surface adhesin A (PsaA) is a streptococcal common protein, and is a vaccine candidate which could be affordable for all countries.